Spark-plug



A. SCHMIDT.

SPARK PLUG. APPLICATION FILED SEPT. 25. I918.

Patented Sept. 7, 1920.

INVENTOR (IIIUQPI QSQIZIYZICII' BY .4 TTORNEY.

UNITED STATES PATENT OFFICE.

ALBERT SCHMIDT, OF FLINT, MICHIGAN, ASSIGNOR T0 CHAMPION IGNITION COMPANY,

OF FLINT, MICHIGAN, A CORPORATION OF MICHIGAN.

SPARK-PLUG.

Application filed September 25, 1918.

To all whom it may concern:

Be it known that I, ALBERT SCHMIDT, a citizen of the United States, and resident of Flint, Genesee county, State of Michigan, have invented certain new and useful Improvements in Spark-Plugs, of which the following is a specification.

The invention relates to improvements in spark plugs as described in the present specification and illustrated in the accompanying drawing that forms part thereof.

One of the objects of the invention is to devise a spark plug which will continually present a clean insulator surface upon which carbon will not deposit, and which therefore will not become short-circuited.

Another object of the invention is to devise a spark plug in which all pockets or recesses where heated gases might find ingress are eliminated and thus the plug is kept as cool as possible.

Another object of the invention is to devise a spark plug in which the entire surface exposed to the products of combustion may be readily cleaned.

Another object of the invention is to devise a spark plug in which it is possible to support the central electrode substantially at the extreme lower end of the plu and leave the upwardly extending portion 0 the electrode quite clear of the insulator, whereby the insulator is free from all strains and stresses due to unequal expansion and contraction of contacting surfaces or members, and thus the life of the insulator is increased to a maximum.

Another object of the invention is to support the electrode within the insulator in such a way that any vibration or jars at the upper end of the electrode will in no manner be transmitted to the insulator at a art thereof liable to fracture or crack.

hese and other objects will more clearly appear from the following description taken in connection with the accompanying drawing.

In the drawing, Figure 1 is a side eleva tion view, partly in section, of a spark plug embodying the invention. Fig. 2 is an end view of the plug as shown in Fig. 1 from the under side. Fig. 3 is a side elevation of a plug similar to that illustrated in Figs. 1 and 2 but showing the invention in a slightly modified form. Fig. 4 is a vertical sectional view of a plug showing a fur- Specification of Letters Patent.

Patented Sept. *7, 1920.

Serial No. 255,579.

ther modified form of the invention and the particularly advantageous arrangement of insulator and electrode permitted thereby. Fig. 5 is a side elevation view of the lower part of the plug partially broken away, showing a still further modified arrangement of the invention.

Like numerals of reference indicate similar parts throughout the several views.

Referring to the drawing, particularly Figs. 1 and 2, 10 is the shell of the plug which may be of any desired form, as well understood in the art, and having the insulator member 11 centrally supported therein, said insulator member, however, terminating as at 12 some distance within the lower end of the plug.

The lower portion of the shell 10 is lined with a mica cylinder 13, which passes up the interior bore of the shell beyond the end 12 of the insulator 11. An electrode 14 is arranged within the insulator 11 and extends upwardly therethrough and beyond at the top, the lower end of said electrode having the enlarged flange 15 and the downwardly extending sparking point 16.

The sparking point of the electrode has the insulator 17 arranged thereon and filling the lower end of the bore of the shell 10, said insulator 17 being retained in the shell by turning over the lower edge flange 18 of the shell.

The insulator 17 further has formed on the lower end thereof concentric ringed ridges 19 which are formed comparatively sharp around their edge and from the center of which the sparking point 20 of the electrode 14 extends and co-acts in a well known manner with the sparking oint 21 arranged on the shell member at t e lower end thereof.

The upper end of the electrode 14 is covered by a tube of mica 22 and a dome men1 ber 23 is arranged on the top of the shell and extends upwardly, having a central orifice 24 therethrough through which the electrode 14 extends and whereon is threaded a suitable terminal nut 25.

It will be understood that the general arrangement of the spark plug is immaterial beyond the fact that the special feature wherein the insulator 17 is formed with the ridged end as described to present the ridged face to the productsof combustion in such a manner as to become comparatively highly heated, at least to such an extent that any hydrocarbon deposit made upon the ridges will be burned off on the finer edge of the ridge, and thus. short-circuiting between the sparking point 20 of the electrode and the lower edge flange 18 of the shell will be effectually prevented.

The amount of space over the ridges, that is, up and down, to be covered with hydrocarbon to properly effect a short-circuit from the sparking. point to the shell proper is made considerably more than ordinary by such ridge formation, and approximately equals that of other spark plug constructions requiring interior chambers and recesses in theshell proper.

It must be noted that in addition to the advantages of the particular form of insu-' the cylinder of mica and supported by the dome as described, whereby a maximum of vibration will occur without the proper arrangement and functioning of the insulator members 11 and 17 being in any manner affected, and of course it is understood that the insulator members 11 and 17, and more particularly the member 17, are only truly efficient when made from a material such as a high-grade porcelain which will retain its dielectric properties and not deteriorate or disintegrate when exposed to an intense heat.

lln the modification shown in .Fig. 3, the general arrangement of the plug is substantially the same as that described with reference to Figs. 1 and 2, except that the extreme 7 lower end of the insulator member 17 on which the ridges 19 are formed is shown substantially hemi-spherical in shape.

The further modification shown in Fig. 4 is of particular interest in that it shows the insulator 26 made in one piece and clamped at the extreme lower end of the shell be tween the flanges 27 and 28, the lower end of the insulator being formed with the single ridge 29 and the upper end extending upwardly in cylindrical form as at 30, the wall of the cylindrical extension gradually decreasing in thickness, giving a flared effect to the interior and a tapered efiect to the exterior thereof.

The electrode 31 is secured as shown at the extreme lower end thereof in the body port on of the insulator 26, and the part extending upwardly through the tubular extension 30 is clear of the wall of the tubular resales extension and supported only at the top thereof in the dome member 23.

In this form of the invention it will be clearly understood that any vibration or shock occurring at the terminal end of the electrode 31 will be in no manner transmitted to the upper end of the insulator, and the effects of any such vibration or shock as received at the lower end of the insulator, where the electrode is supported, will be so reduced as to in no manner affect the same to cause fracture or breakage.

It will also be understood that this type of plug makes for a very simple and inexpensive arrangement and the length of insulator and metal in contact with one another is so reduced that expansion and contraction will not cause any fracture or shortcircuiting.

In the further modification shown in Fig. 5, it is illustrated wherein the insulator member 33 may be supported in the center or body part of the shell and the lower end thereof extend downwardly from the body or center part of the shell to the lower end thereof and have the ridges 3 1 formed thereon the same being immediately flush with the end of the shell, whereby theyv are properly guarded from contact with any object which might cause them to break and yet where they may be readily cleaned as is the case with the other modifications shown.

It will be obvious to those skilled in the art that many modifications and changes may be made without departing from the spirit and scope of the invention.

Having now described my invention what ll claim as new and desire to secure by Letters Patent is:

1. A spark plug comprising a hollow external shell or casing; an insulator secured in place within said casing and located at the lower end thereof and filling the same at the said lower end, so as to prevent gases from accumulating between said casing and said insulator, and which insulator extends beyond the lower or inner end of said casing; a plurality of concentrically arranged ridges formed upon the exposed inner end of said insulator, and which ridges are located beyond the end of said shell or casing; and an electrode extending through a passage provided for it in said insulator.

2. spark plug comprising a hollow external shell or casing; an insulator secured in place within said casing and located at the lower end thereof and filling the same at the said lower end, so as to prevent gases from accumulating between said casing and said insulator, and which insulator extends beyond the lower or inner end of said casing; a plurality of concentrically arranged ridges formed upon the exposed inner end of said insulator, and which ridges are 10- cated beyond the end of said shell or casing; a second insulator located within said casing and above said first mentioned insulator, and which second insulator terminates below the upper end of said shell or-casing; and an electrode extending through passages provided in said insulators and having a flange which lies between the adjacent ends of said insulators.

3. A spark plug comprising a hollow external shell or casing;-an insulator secured in place within said casing and located at the lower end thereof and filling the same shell or casing; flanges integral with said shell or casing and extending inward and over the ends of said two insulators to thereby permanently secure said insulators in placewithin said shell; and an electrode extending through passages provided for it in said two insulators, and which electrode is provided with a flange which lies between the adjacent ends of said insulators.

4. A spark plug comprising an external shell or casing; an insulator secured in place within the lower end of said casing and filling the same at said lower end so as to pre vent gases from accumulating between said casing and insulator, and which insulator is provided with a central upwardly extending portion smaller in diameter than the interior of the upper portion of said casing and which reduced portion extends above the upper end of said casin a passage extending longitudinally 0% said insulator; and an electrode extending through said passage and fitting tightly therein at the lower end of said passage, but which elecand which reduced portion extends above.

theupper end of said casing; a passage extending longitudinally of said insulator; an electrode extending through said passage and fitting tightly therein at the lower end of said passage, but which electrode 1s smaller than said passage throu bout the greater part of the length thereo a dome resting upon said external shell or casing and surrounding the upper end of said insulator and having a hole through which the upper end of said electrode extends; and a nut in threaded engagement with the upper end of said electrode.

6. A spark plug comprising an external shell or casing; an insulator secured in place within the lower end of said casing and filling the same at said lower end so as to prevent gases from accumulating between said casing and insulator, and which insulator is provided with a central upwardly extending portion smaller in diameter than the interior of the upper portion of said casing and which reduced portion extends above the upper end of said casing; a passage extending longitudinally of said insulator; an electrode extending through said passage and fitting tightly therein at the lower end of said passage, but which electrode is smaller than said passage throughout the greater part of the len h thereof; and a plurality of concentrical y arranged rid es formed upon the exposed inner end-o said insulator, and which ridges are located beyond the inner end of said shell or casing.

In testimony whereof I afiix my signature.

ALBERT SCHMIDT. 

